function [g,info] = nsgabwin(g,a,M);
%NSGABWIN  Compute a set of non-stationary Gabor windows from text or cell array
%   Usage: [g,info] = nsgabwin(g,a,M);
%
%   `[g,info]=nsgabwin(g,a,M,L)` computes a window that fits well with
%   time shift *a*, number of channels *M* and and transform length *L*.
%   The window itself is as a cell array containing additional parameters.
%
%   The window can be specified directly as a cell array of vectors of
%   numerical values. In this case, `nsgabwin` only checks assumptions
%   about transform sizes etc.
%
%   `[g,info]=nsgabwin(g,a,M)` does the same, but the windows must be FIR
%   windows, as the transform length is unspecified.
%
%   The window can also be specified as cell array. The possibilities are:
%
%     `{'dual',...}`
%         Canonical dual window of whatever follows. See the examples below.
%
%     `{'tight',...}`
%         Canonical tight window of whatever follows. See the examples below.
%
%   The structure *info* provides some information about the computed
%   window:
%
%     info.gauss    True if the windows are Gaussian.
%
%     info.tfr      Time/frequency support ratios of the window. 
%                   Set whenever it makes sense.
%
%     info.isfir    Input is an FIR window
%
%     info.isdual   Output is the dual window of the auxiliary window.
%
%     info.istight  Output is known to be a tight window.
%
%     info.auxinfo  Info about auxiliary window.
%   
%     info.gl       Length of windows.
%
%     info.isfac    True if the frame generated by the window has a fast
%                   factorization.
%
%   See also: filterbank, filterbankdual, filterbankrealdual

% Assert correct input.
if nargin<2
  error('%s: Too few input parameters.',upper(mfilename));
end;

if ~iscell(g)
  error('%s: Window g must be a cell array.',upper(mfilename));
end;

if isempty(g)
  error('%s: Window g must not be empty.',upper(mfilename));
end;

info.isdual=0;
info.istight=0;

% To stop the madness, all index/lengths vectors are converted to columns
a=a(:);
M=M(:);

if ischar(g{1})
    winname=lower(g{1});
    switch(winname)
      case {'dual'}
        [g,info.auxinfo] = nsgabwin(g{2},a,M);
        g = nsgabdual(g,a,M);
        info.isdual=1;
        
      case {'tight'}
        [g,info.auxinfo] = nsgabwin(g{2},a,M);    
        g = nsgabtight(g,a,M);
        info.istight=1;
        
      otherwise
        error('%s: Unsupported window type %s.',winname,upper(mfilename));
    end;
end;

info.gl=cellfun(@length,g);
info.gl=info.gl(:);

info.L=sum(a);
info.a=a;
N=length(a);

if N~=numel(g)
  error(['%s: The number of time-shifts %i must match the number of windows ' ...
         '%i.'],upper(mfilename),N,numel(g));
end;

if numel(M)~=1 && numel(M)~=N
    error(['%s: The arrays "a" and "M" must be equally long. ' ...
           'numel(a)=%i, numel(M)=%i.'],upper(mfilename),N,numel(M));
end;

if any(info.L<info.gl)
    error('%s: Window is too long.',upper(mfilename));
end;

info.ispainless=all(info.gl<=M);
info.isuniform=std(M)==0;

info.isfac=info.ispainless || (info.isuniform && rem(info.L,M(1))==0);

if info.isuniform
    info.M=repmat(M(1),N,1);
else
    info.M=M;
end;
